The present invention relates generally to the application of images onto articles of commerce, particularly onto articles of clothing, and relates more particularly to the application of images onto such articles of commerce using heat-transfer imaging techniques.
In recent times, there has been considerable growth in the industry devoted to the consumer-personalization of clothing items, such as T-shirts, sportswear and the like. The creation of such personalized items typically takes place using either one of two different techniques, namely, by directly printing a personalized image onto the article of clothing or by printing an image onto a transfer sheet and then transferring the printed image from the transfer sheet to the intended article using heat and pressure.
Consumer-personalization via direct printing is typically performed in specialty shops as a “do-it-for-you” approach. According to this approach, a consumer, using an e-commerce web server, sends to the shop a graphic image in digital format, together with information on the type, color and size of clothing article. The shop then electronically transforms the graphic image into a standard graphic format and subsequently transmits the formatted image to a direct-to-fabric industrial printer for a final printing. Before shipping the personalized item to the consumer, the shop may use heat-pressing to further fix the image.
It should be noted that the aforementioned direct printing technique results in only the graphic image being printed on the article, with the fabric material of the article, itself, providing the background for the image.
The types of printers used in the above-described direct printing technique are typically high-output, digital, ink-jet printers. Although such printers are capable of providing photo-realistic images on T-shirts and the like, they are limited by a number of drawbacks: First, when reactive dyes are used that bind chemically to fabrics, such dyes require specialized pre- and post-processing that makes small varied orders uneconomical. Second, when pigment-based inks are used that have limited binding to fabrics, the images are thin and not very durable after many wash/dry cycles. Third, because the image is printed directly onto the article, the printed resolution of the image is typically limited by how fine or course the article is. Fourth, there is typically a high capital spending associated with using very specialized printers. Fifth, the printing process involves expensive consumables, such as inks.
Consumer-personalization via image transfer typically involves the use of a heat-transfer sheet as an intermediate holder of a graphic image. The image transfer technique enables consumer-personalization to be performed not only by specialized shops but also by the consumer, herself, using common household articles, such as a desktop, ink-jet printer for printing and an iron for heat-transfer. Background information relating to the image transfer technique may be found in the following illustrative patents and published patent applications, all of which are incorporated herein by reference: U.S. Pat. No. 7,160,411, inventors Williams et al., which issued Jan. 9, 2007; U.S. Patent Application Publication No. US 2006/0172094 A1, inventors Shi et al., which was published Aug. 3, 2006; U.S. Pat. No. 6,139,672, inventors Sato et al., which issued Oct. 31, 2000; U.S. Pat. No. 4,773,953, inventor Hare, which issued Sep. 27, 1988; and U.S. Pat. No. 4,294,641, inventors Reed et al., which issued Oct. 13, 1981.
The heat-transfer sheet used in the aforementioned image transfer technique typically comprises a non-transferable support, such as a release-coated paper or a film carrier, and a heat-transferable portion, which may include a polymer-based coating that undergoes melting or softening when heat is applied, with the graphic image typically being reverse-printed directly onto the exposed surface of the heat-transferable portion. Alternatively, the aforementioned polymer-based coating onto which the image is printed may be omitted from the heat-transfer sheet as the heat-transfer sheet may consist solely of the non-transferable support, e.g., the release-coated paper or the film carrier. In this latter case, the heat-transferable part typically consists of the ink layer that is delivered by the printing device and that forms the graphic image.
The graphic image applied to the heat-transfer sheet may be printed using analog printing techniques or digital printing techniques. Examples of suitable analog printing techniques include letterpress, flexography, gravure, reverse gravure, off-set lithography (wet and dry), flat and rotary screen, hot and cold stamping, pens and markers. Such techniques are capable of applying a thick, mechanically-durable, graphic image. Examples of suitable digital printing techniques include using common desktop and wide format shop printers, such as ink-jet, toner-based laser, ion or electron charge deposition printing, copy machines, phaser and direct thermal or thermal transfer printers, etc. In general, digital printing techniques result in a much smaller amount of ink or toner being printed. Consequently, if a digital printing technique is used, the transfer sheet typically includes the polymer-based meltable coating (as opposed to lacking such a coating and having the image printed directly on the non-transferable support) as such a coating is used to absorb or to hold in place the graphic image. In certain instances, a combination of both analog and digital printing techniques may be used on a heat-transfer sheet.
When performing image transfer on clothing items using heat-transfer sheets that include a polymer-based meltable coating, it is often desirable to transfer only the printed areas of the transfer sheet and not the unprinted background areas. This is because the polymer-based meltable coating can leave a visible background halo around the printed image on the fabric. Such a halo may be aesthetically undesirable.
One approach to the foregoing problem of a background halo has been to mechanically remove the background polymer-based coating from the printed heat-transfer sheet prior to heat-transfer. The mechanical removal of the coating is performed using a digitally-controlled mechanical cutter that cuts around the graphic design image. After cutting, the coating from the extraneous non-printed areas is removed. The aforementioned process is known in the art as mechanical weeding. Unfortunately, mechanical weeding can be complicated and slow, especially when applied to very fine and detailed graphic designs.
An alternative approach to mechanical weeding is disclosed in U.S. Patent Application Publication No. US 2006/0019043 A1, inventor Kronzer, published Jan. 26, 2006, which is incorporated herein by reference. In the aforementioned publication, there is disclosed a heat transfer material kit that includes a first image transfer material and a second image transfer material, the first image transfer material including a printable non-porous surface, the second image transfer material including an outer layer having a film-forming binder and thermoplastic particles. A method of using the kit involves (a) imaging the substantially non-porous printable surface of the first image transfer material to form an imaged surface having printed and unprinted areas; (b) positioning the outer layer of the second image transfer material adjacent to the imaged surface; (c) transferring a portion of the outer layer of the second image transfer material to the printed area on the first image transfer material while transferring a lesser portion of the outer layer of the second image transfer material to the non-printed area on the first image transfer material to form a coated imaged surface having a non-printed area with less coating than the printed area; and (d) transferring the coated image to a substrate.
Unfortunately, the approach of the above-described Kronzer publication is made complicated by the necessity of providing two different types of image transfer materials and by the limited utility of the approach to toner-based printers. In addition, the half-toning process used by laser printers to achieve the grey scale could make the above method difficult to work on lighter colored images where toner density is lower.